The present invention relates generally to medical devices, and more particularly to an apparatus and method for using an ultrasonic medical devices operating in a transverse mode emulsification of endovascular materials by causing tissue fragmentation of occlusion materials. The invention also relates to an apparatus emitting ultrasonic energy in transverse mode used in combination with an elongated flexible catheter wire, wherein the probe is rapidly attachable to and detachable from the ultrasonic energy source component of the device.
Vascular occlusions (clots or thrombi and occlusional deposits, such as calcium, fatty deposits, or plaque) result in the restriction or blockage of blood flow in the vessels in which they occur. Occlusions result in oxygen deprivation (xe2x80x9cischemiaxe2x80x9d) of tissues supplied by these blood vessels. Prolonged ischemia results in permanent damage of tissue that can lead to myocardial infarction, stroke, or death. Targets for occlusion include coronary arteries, peripheral arteries and other blood vessels. The disruption of an occlusion or thrombolysis can be effected by pharmacological agents and/or or mechanical means.
Ultrasonic probes are devices which use ultrasonic energy to fragment body tissue (see, e.g., U.S. Pat. Nos. 5,112,300; 5,180,363; 4,989,583; 4,931,047; 4,922,902; and 3,805,787) and have been used in many surgical procedures. The use of ultrasonic energy has been proposed both to mechanically disrupt clots, and to enhance the intravascular delivery of drugs to clot formations (see, e.g., U.S. Pat. Nos. 5,725,494; 5,728,062; and 5,735,811). Ultrasonic devices used for vascular treatments typically comprise an extra-corporeal transducer coupled to a solid metal wire that is attached to a plurality of wires at the distal end, that is then threaded through the blood vessel and placed in contact with the occlusion (see, e.g., U.S. Pat. No. 5,269,297). In some cases, the transducer is delivered to the site of the clot, the transducer comprising a bendable plate (see, U.S. Pat. No. 5,931,805).
The ultrasonic energy produced by an ultrasonic probe is in the form of very intense, high frequency sound vibrations that result in powerful chemical and physical reactions in the water molecules within a body tissue or surrounding fluids in proximity to the probe. These reactions ultimately result in a process called xe2x80x9ccavitation,xe2x80x9d which can be thought of as a form of cold (i.e., non-thermal) boiling of the water in the body tissue, such that microscopic bubbles are rapidly created and destroyed in the water creating cavities in their wake. As surrounding water molecules rush in to fill the cavity created by collapsed bubbles, they collide with each other with great force. This process is called cavitation and results in shock waves running outward from the collapsed bubbles which can fragment or ablate material such as surrounding tissue in the vicinity of the probe.
Some ultrasonic probes include a mechanism for irrigating an area where the ultrasonic treatment is being performed (e.g., a body cavity or lumen) to wash tissue debris from the area. Mechanisms used for irrigation or aspiration described in the art are generally structured such that they increase the overall cross-sectional profile of the probe, by including inner and outer concentric lumens within the probe to provide irrigation and aspiration channels for removal of particulate matter. In addition to making the probe more invasive, prior art probes also maintain a strict orientation of the aspiration and the irrigation mechanism, such that the inner and outer lumens for irrigation and aspiration remain in a fixed position relative to one another, which is generally closely adjacent the area of treatment. Thus, the irrigation lumen does not extend beyond the suction lumen (i.e., there is no movement of the lumens relative to one another) and any aspiration is limited to picking up fluid and/or tissue remnants within the defined distance between the two lumens.
Another drawback of existing ultrasonic medical probes is that they typically remove tissue relatively slowly in comparison to instruments that excise tissue by mechanical cutting. Part of the reason for this is that existing ultrasonic devices rely on a longitudinal vibration of the tip of the probe for their tissue-disrupting effects. Because the tip of the probe is vibrated in a direction in line with the longitudinal axis of the probe, a tissue-destroying effect is only generated at the tip of the probe. One solution that has been proposed is to vibrate the tip of the probe in a direction other than perpendicular to the longitudinal axis of the probe, in addition to vibrating the tip in the longitudinal direction. It is proposed that such motions will supplement the main point of tissue destruction, which is at the probe tip, since efficiency is determined by surface area of the probe tip. For example, U.S. Pat. No. 4,961,424 to Kubota, et al. discloses an ultrasonic treatment device that produces both a primary longitudinal motion, and a supplementary lateral motion of the probe tip to increase the tissue disrupting efficiency. The Kubota, et al. device, however, still relies primarily on the tip of the probe to act as a working surface. The ancillary lateral motion of the probe is intended to provide an incremental efficiency for the device operation. Thus, while destruction of tissue in proximity to the tip of the probe is more efficient, tissue destruction is still predominantly limited to the area in the immediate vicinity at the tip of the probe. The said invention is therefore limited in its ability to ablate tissue within inner surfaces of cylindrical blood vessels, for example, in vascular occlusions. U.S. Pat. No. 4,504,264 to Kelman discloses an ultrasonic treatment device containing a probe that is capable of longitudinal vibrations and lateral oscillation. The said invention is intended to improve the efficiency of ultrasonic tissue removal by providing a dual function of a fragmentation and a cutting device. Tissue fragmentation is caused primarily by oscillating the tip of the probe in addition to relying on longitudinal vibrations of the probe, while the lateral oscillations. Tissue fragmentation is caused primarily at the tip of the device, while the oscillatory motion can be employed by the surgeon to cut tissue, thereby increasing efficiency of surgical procedures. The foregoing inventions also require complex instrument design that require incorporation of a plurality of electrodes, ultrasound frequency generating elements, switches or voltage controllers.
The longitudinal probe vibration required for tissue ablation in prior art devices necessitates the probe lengths to be relatively short, since use of long probes result in a substantial loss of ultrasonic energy at the probe tip due to thermal dissipation and undesirable horizontal vibration that interferes with the required longitudinal vibration.
Although narrow probe diameters are advantages especially for negotiation through narrow blood vessels and occluded arteries, the utilization of such probes have been precluded by inability to effectively control the vibrational amplitude of thin probes, that result in potential damage to the probe and greater risk of tissue damage resulting from their use. The use of narrow-diameter probes have been disclosed in the art for providing greater maneuverability ease of insertion in narrow blood vessels. U.S. Pat. No. 4,920,954 to Allinger discloses a narrow diameter ultrasonic device wherein a rigid sleeve is used to prevent transverse vibrations U.S. Pat. No. 5,380,274 discloses a narrow diameter probe for improved longitudinal vibration having a sheath to inhibit transverse vibration U.S. Pat. No. 5,469,853 to Law discloses a thin, longitudinally vibrating ultrasonic device with a bendable sheath that facilitates directing the probe within narrow blood vessels. While the prior art has focused on the need for using sheaths on thin ultrasonic devices, their use has been entirely to prevent transverse vibrations of the device and to protect such devices from damage resulting from such vibrations.
Based on the aforementioned limitations of ultrasonic probes in the art, there is a need for ultrasonic probe functioning in a transverse mode that further obviates the shortcomings of that further overcomes limitations imposed by of narrow diameter requirements for efficient operation of such probes for rapid tissue ablation. Transversely vibrating ultrasonic probes for tissue ablation are described in the Applicant""s co-pending provisional applications U.S. Ser. Nos. 60/178,901 and 60/225,060, and 20563/1010 (Attorney Docket No.) which further describe the design parameters for such a probe its use in ultrasonic devices for tissue ablation. The entirety of these applications are herein incorporated by reference.
This limitation has precluded the use of ultrasonic tissue ablation devices in surgical procedures wherein access to vascular occlusion requires traversing an anatomically lengthy or sharply curved path along tubular vessels. The self-suggesting idea of effecting ultrasonic transmission through a plurality of flexible thin wires has been found impracticable because (1) relatively high power (xcx9c25 watts) is required to deliver sufficient energy to the probe tip, and (2) such thin wires tend to perform buckling vibrations, resulting in almost the entire ultrasonic power introduced in the probe is dissipated during its passage to the probe tip.
The relatively high-energy requirement for such devices causes probe heating that can cause fibrin to re-clot blood within the occluded vessel (thermally induced re-occlusion). Additionally, the elevation in probe temperature is not just limited to probe tip, but also occurs at points wherein the narrow diameter wire probes have to bend to conform to the shape of the blood vessel, thereby limiting causing probe damage and limiting its reuse.
A single thick wire probe on the other hand, cannot negotiate the anatomical curves of tubular arterial and venous vessels due to its inflexibility, and could cause damage to the interior wall of such vessels. Currently, such exchange procedures are not possible because ultrasonic probes used in endovascular procedures are permanently attached to the transducer energy source or a probe handle coupled to such source, such as for example, by welding, thereby precluding probe detachment. Moreover, since probe vibration in such devices in a longitudinal mode, i.e. along the probe longitudinal axis, a proximal contact with the transducer or the probe handle segment connect is essential to prevent a xe2x80x9chammeringxe2x80x9d effect that can result in probe damage.
The present invention relates to an ultrasonic device comprising an elongated catheter probe vibrating substantially in a direction transverse to the probe longitudinal axis and capable of emulsifying endovascular materials, particularly tissue. The diameter of the catheter probe is sufficiently small to confer flexibility on said probe so as to enable its negotiation through narrow and anatomically curved tubular vessels to the site of an occlusion that is remotely located from the point of probe insertion into the body. The catheter probe of the invention is designed to work in conjunction with standard vascular introducers and guide catheters. Another aspect of the invention is to provide a rapidly attachable and detachable or xe2x80x9cquick attachment-detachmentxe2x80x9d means (referred to hereinafter as xe2x80x9cQADxe2x80x9d) for the catheter probe to and from the ultrasonic energy source, thereby enabling manipulation and positioning of the probe within the body vessel without being limited by the relatively bulky energy generating source. The catheter probe of the invention additionally comprises a concentric tubular sheath to facilitate fluid irrigation, aspiration of ablated tissue fragments and introducing a therapeutic drug to the site of occlusion.
An ultrasonic probe vibrating in a transverse mode for removal of occlusions in blood vessels has been disclosed in applicants"" co-pending application Ser. No. 09/776,015, the entireity of which is incorporated herein as reference. The said reference discloses an ultrasonic device in which a transducer is connected to a probe with a flexible tip capable of vibrating in a direction transverse to the probe longitudinal axis. With such a probe a situation may arise where it will be desirable to utilize an elongated probe resembling a catheter guide-wire probe to make possible exchange procedures often used in angioplasty.
In general, it is an object of the invention to provide an ultrasonic medical device for removing vascular occlusions comprising a detachable elongated catheter guide wire probe capable of vibrating in a transverse mode.
Another object of the invention is to provide an elongated guide wire probe of the above character of the above character that is and comparable in size to existing guide wires.
Another object of the invention is to provide an elongated guide wire probe of the above character which includes a quick attachment-detachment means to an ultrasound energy source.
Another object of the invention is to provide an elongated guide wire probe of the above characteristics which is compatible with the existing guide wire exchange systems.
Another object of the invention is to provide a probe attachment-detachment means comprising a coupling assembly.
Yet another object of the invention is to provide a guide wire of the above character which can be inserted, retracted or torqued in a detached mode to prevent interference with the probe handle and the ultrasound transducer.
A further object of the invention is to provide a guide wire assembly and system and apparatus utilizing the same of the above character, which permits intravascular ultrasonic tissue ablation.